Buoyancy device for a water surface craft



Feb 8, 1966 M. JUSTENIEN 3,233,574

BUOYANCY DEVICE FOR A WATER SURFACE CRAFT Filed June 16, 1964 4 Sheets-Sheet 1 Feb. 3, 11966 M. JUSTINIEN 3,233,574

BUOYANCY DEVICE FOR A WATER SURFACE CRAFT Filed June 16, 1964 4 Sheets-Sheet 2 Feb. 8, 1966 M. JUSTINIEN BUOYANCY DEVICE FOR A WATER SURFACE CRAFT 4 Sheets-Sheet 5 Filed June 16, 1964 Feb. 8, 1966 M. JUSTINIEN BUOYANGY DEVICE FOR A WATER SURFACE CRAFT 4 Sheets'Sheet 4 Filed June 16, 1964 3,233,574 BUOYANCY DEVICE FOR A WATER SURFACE CRAFT Marcel Justinien, Paris, France Filed June 16, 1964, Ser. No. 375,580 Claims priority, application France, June 26, 1963, 8,723, Patent 1,362,315; Apr. 9, 1964, 8,916 Claims. (Cl. 115-19) This invention relates to buoyancy devices.

According to the present invention there is provided a buoyancy device for a water surface craft, comprising a screw having a volumetric water displacement of less than one half of its own volume for carrying said craft on the water and which is mounted rotatably on said craft.

In order that the invention may be clearly understood and readily carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

FIGURE 1 shows a fragmentary side view of a buoyancy-imparting and driving screw propeller of a water surface craft,

FIGURE 2 is a fragmentary axial sectional View through the screw propeller,

FIGURE 3 is a fragmentary perspective view of the craft,

FIGURE 4 shows a side view of a modified version of the screw propeller,

FIGURE 5 is a fragmentary axial sectional view through the version of FIGURE 4,

FIGURE 6 is a fragmentary side view of another modified version of the screw propeller,

FIGURE 7 is a sectional view taken along line 4-4 of FIGURE 6,

FIGURE 8 illustrates sectional views 5-5 of FIGURE 6,

FIGURE 9 is a plan view of a development of a portion of the version of FIGURE 6, and

FIGURE 10 is a front view of a modified version of the craft, in this case a canoe. FIGURES l and 2 show a buoyancy-imparting and driving screw propeller designated, as a whole, by the reference numeral 1. The screw propeller may have one or more spiral members as may be suitable having regard to buoyancy, speed, and other considerations. The illustrated propeller has two spiral members, 1a and 1b which extend co-axially around a driving shaft 2 and which are fixed either directly to the shaft 2 or to a sleeve 3 extending co-axially on the shaft 2 and fixed thereto.

The spiral mernbers 1a and 1b are hollow and are made from sheet-metal appropriately profiled and folded, or from a plastic material. The cross-sectional profile of each spiral member 1a and 1b is, as shown in FIGURE 2, a V-shaped profile having a rounded apex, but it is possible to employ other cross-sectional profiles.

The dimensions of the spiral members of the propeller are, both in respect of their crosssection and of their diameter, so chosen that they provide for buoyancy such that normally the members 1a and 1b are immersed to the level N which is located below the sleeve 3, the members 1a and 1b being the only parts of the craft which are immersed in the water. Consequently, it is only the members 1a and 1b which provide the volume which insures the buoyancy of the surface craft. There is therefore a considerable difference between the maximum external diameter of the sleeve 3 and that of the members In and 1b.

It will be clear that the screw must have a volumetric water displacement which is less than half of its own volume. The screw may be hollow or, if solid, made from a material the specific density of which is low. Also,

taken along lines United States Patent 0 each spiral member could be in the form of an inflatable envelope.

As shown in FIGURE 1 the ends of the shaft 2 are mounted to rotate in bearings 4, for example ball bearings, from which extends the super-structure 5 of the water craft.

The water craft could be equipped with a single propeller 1 and with lateral balancing means, but it is preferably equipped with a plurality of parallel propellers 1, for example two propellers 1 (see FIGURE 3). It would of course be possible to align a plurality of propellers 1 in two parallel alignments.

The shaft or shafts 2 and the propeller(s) "1 are driven by any suitable source of energy and suitable driving system.

Finally, the possibility is not excluded of using the screw simply as a buoyant and idling screw, in which case the screw is no longer driven, the driving of the craft being carried out by independent means acting in traction or in propulsion on the water craft.

Referring to FIGURES 4 and 6, the propeller providing buoyancy and driving power is now designated, as a whole, by the reference numeral 6. The propeller has two spiral members 6a and 6b which are either fixed coaxially to a sleeve 7 which is fast with a shaft 8, as shown, or are fixed directly to the shaft 8. The latter is mounted at both ends for rotation in bearings 9 carried on the superstructure 10 of the water craft. Reference numeral 11 designates a pinion keyed on the shaft 8 and a driving chain engaging with the pinion.

The spiral members shown are hollow, but it should be emphasized that the propeller could be solid and of a material of low specific density.

The leading and trailing parts of the members 6a and 6b are of such form as to ensure good progr-essivity, in respect of their sectional dimensions and their volume, from the leading extremities 6c of the members to the locations tie at which intermediate parts of constant external peripheral radius commence, and from the locations 62 at which the intermediate parts finish to the trailing extremities 6d. The external peripheral diameter of the members 6a and 6b at the extremities 6c and 611 is approximately equal to that of the sleeve 7.

The pitch P of the members 6a and 6b is two to three times the maximum external peripheral diameter D of the members.

The lengths m and n over which the cross-sections of the members do and 6b gradually change correspond to at least one half of the pitch P and preferably correspond to the pitch P. t

In the version of FIGURES 6 and 7, the lengths m and n correspond substantially to one pitch P and the degree of progressivity is such that between the points 6g at which the members attack the water surface and the points 6 at which the intermediate parts commence, there is an axial distance 0 corresponding substantially to one half-pitch, and an angular distance of substantially The turns 6:: and 6b have fiat external peripheral faces of constant width over the intermediate parts but of gradually diminishing width over the leading parts and the trailing parts, the faces being of long, narrow triangular shape 6e (FIGURE 9) over the leading and trailing parts, the apex of each triangle being located at the relevant extremity of the members. This shape 6e facilitates sliding of the screw in the water, improves buoyancy and diminishes the draught. The external per-ipheral edges of the members 6a and 6b are rounded.

The members 6a and 612 have substantially trapezoidal cross-sections, the cross-sectional dimensions decreasing at the ends over the leading and trailing parts (FIGURE 8).

The cross-section dimensions of the turns are relatively large and the intermediate parts have a height h equal to the width b of the flat external peripheral faces of the intermediate parts, the identical dimensions 11 and b each being in the approximate ratio of 2:5 relatively to the diameter D. The width B of the inner peripheries of the intermediate parts is in the approximate ratio of 1:2 relatively to the diameter D.

With these conditions, there is obtained a propeller which provides for the maximum degree of buoyancy with the minimum draught and consequently with a smaller dynamic water displacement.

It should be emphasized that, as can be seen from FIGURE 7, the member cross-section entering the water increases with a progression which is gradual, and gives the minimum water displacement and resistance.

It is possible to consider, having regard to the small draught, that the propeller to some extent rolls on the water or in a small water depth. Thus, what is concerned is a propeller which is entirely suitable for its supporting and propelling role and which may be considered to constitute an integral propeller.

The resistance of the water to the advance of the craft is consequently diminished very considerably, in such manner that it is possible to envisage the propulsion of the craft at high speed by means of a relatively small driving power. Production of boats so propelled and containing two to six places for passengers, is visualized which makes use of the mass production resources oi the automobile industry, because certain automobile parts, e.g. the engine, the clutch and the gear box, may be utilized with a minimum of modifications and even without any modifications whatsoever. In this connection, FIGURE illustrates a front view of a canoe having two parallel propellers of opposite hand.

The external peripheries of the spiral members may have, over all or a part of their developed length and preferably in the median portion of their width, a ridge 6 of triangular section, as illustrated in chain lines in FlG- URE 5, for the purpose of improving the penetration and sliding effect in water.

The rated driving speedof the propeller is relatively low, of the order of 400 to 700 rpm. for example, this rated speed being decided in each case taking into account the large pitch of the turns and so as to prevent the occurrence of an excessively large resistance of the Water to the spiral members.

One or more brakes 12 are provided in such manner as to act on the shaft 8 or on the sleeve 7 In the case of a :craft comprising two parallel propellers, by braking one of the propellers relatively to the other, a change in direc tion is produced.

I claim:

1. A buoyancy device for a water surface craft, comprising at least one hollow spiral screw member, and a hollow screw axle means coaxial with said member and having said member fixed thereto for being mounted rotatably on said craft, said member providing a buoyancy for maintaining said axle means normally above water level during use, said screw member including turns having a pitch which is 23 times the maximum diameter thereof, said screw member including a central portion wherein said turns have a maximum and constant diameter and cross-sectional area and end portions wherein the turns progressively increase towards said central portion in diameter and cross-sectional area, said turns having a cross-section tapering radially outwards and having in the central portion a height in the ratio of about 1:25 with respect to the maximum diameter.

2. A device as claimed in claim 1, wherein the turns have a triangular cross-section.

3. A device as claimed in claim 1, wherein the turns have a trapezoidal cross-section.

4. A device as claimed in claim 1, comprising a shait extending through said axle means, and a brake operatively associated with said shaft.

5. A device as claimed in claim 1, comprising two hollow screw members and associated axle means and brakes operatively associated with each said axle means.

References Cited by the Examiner UNITED STATES PATENTS 2,400 12/1841 Wells -88 53,316 3/1866 Masnata -157 512,186 1/1894 Getchell 170'157 636,495 11/ 1899 Dawley 1l5-38 957,056 5/1910 Haynes 115- 38 1,830,985 11/1931 Dreier 170-157 MILTON BUCHLER, Primary Examiner.

R. G. BESHA, A. E. CORRIGAN, Assistant Examiners. 

1. AN BUOYANT DEVICE FOR A WATER SURFACE CRAFT, COMPRISING AT LEAST ONE HOLLOW SPIRAL SCREW MEMBER, AND A HOLLOW SCREW AXLE MEANS COAXIAL WITH SAID MEMBER AND HAVING SAID MEMBER FIXED THERETO FOR BEING MOUNTED ROTATABLY ON SAID CRAFT, SAID MEMBER PROVIDING A BUOYANCY FOR MAINTAINING SAID AXLE MEANS NORMALLY ABOVE WATER LEVEL DURING USE, SAID SCREW MEMBER INCLUDING TURNS HAVING A PITCH WHICH IS 2-3 TIMES THE MAXIMUM DIAMETER THEREOF, SAID SCREW MEMBER INCLUDING A CENTRAL PORTION WHEREIN 